Another way to think about it is: my average comment quality, if I commented on everything I read, would be very low. For most things I just don't have that much to add. So, for most things, I don't comment. Nothing to add? I just move on. The nature of hot button issues though is that they are more likely to elicit comments. They're lowering that innate "Do I have anything to add?" threshold. The result is that average comment quality declines - but their still could be good comments.
Writing this makes me think about a different approach than I'm seeing suggested in other comments here. Less rules and moderation based, and more sorting based. Up and down votes aren't quite right, you get reddit and echo Chambers. But, they aren't entirely wrong either. You need a way to elicit lots of comments (hot button issues) and mitigate the bad ones.
Ultimately a large part of this problem is a total lack of diversity and heavily cis male white perspective here. Tech in general suffers from lack of diversity and it shows. Fixing this would help at least balance the threads a bit and maybe open some minds. I'm cis white male too ¯\_(ツ)_/¯ . we need other voices.
It might not be possible, or pointless, to have a conversation when people live in alternate realities or hold plainly racist, sexist, non factual views.
I do think these topics are important though.
Gender, race, & immigration are great examples of 'political' topics that also tie into what most in this thread feel HN should focus on: tech/startups. These topics are important in discussing hiring, company culture, human rights etc.